James avaed packard



(No Model.)

J. W. PACKARD.

ELECTRICAL TESTING APPARATUS.

10.890818 Patented 008. 2, 1888.

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UNITED STATES FFTQE@ PATENT ELECTRICAL TESTING APPARATUS.

SPECIFICATION forming part of Letters Patent No. 390,3l0I dated Qetober2, 1888.

Application tiled May 4, 1888. Serial No. 972.803.

To ctZZ whom, it may concern.'

Be it known that I, J AMES WARD PACKARD, a citizen of the United States,residing at New York, in the county of New York and State of New York,have invented certain new and useful Improvements in Electrical TestingApparatus; and I do hereby declare the following to be a full, clear,and exact description of the invention, such as will enable othersskilled in the art to which it a1 pcrtains to make and use the same.

My invention consists in asuitable arrange ment of electrical circuitsand contact-making devices by which a circuit which is being suppliedwith a current from any suitable source for the purpose of varying itsresistance may be cut out from such source of current and thrown intocircuit with a suitable testing device without moving any of the variousparts of the apparatus other than the lever of the cut-out or switch.

The drawing represents my apparatus as it may be employed in the processof treating the carbon strips which are to be used in the manufacture ofincandescent electric lamps. C is such carbon strip immersed in thecarbon solution contained in tank T. From the dynamo D, or othersuitable source of electricity, the current Vfollows the direction ofthe arrow through the contact E', the branch A of the cut-out lever, thetrunnion R, the standard S, the binding-post K,th rough the carbon C,back through the bindingpost-K, the standard S', through its trunnion tothe branch A'Z of the cut-out lever, and thence by way of the contact Eto the other brush of the comniutator of the dynamo The passage of thecurrent through the carbon C while the latter' is immersed in the carbon solution in the tank T causes the carbon to deposit upon the strip,and thus increasing its cross section it gradually diminishes itselectrical resistance. It is desirable to test this electricalresistance from time to time Without removing the carbon strip from thetank or receiver in which it may be placed. To do this I have devisedthe following arrangement of circuits and contact making pieces,illustrated in the drawing, and now to be described.

To test the carbon in the manner desired, the operator presses down uponthe button at (No model.)

the end of the branch A of the cut--out lever. Thisl first raises thebranches A/ and A2 from off the contactpieces E' E, and thus cuts outthe source of supply represented by the dynamo D. Continued movement ofthe cut-out lever brings the branches A A2 against the contactpieees FF', thus throwing the carbon Cinto circuit with the connections VV/,which introduce the said carbon C into the circuit of one of thebranches of the W'heatstone bridge, 1 2. In the other branch of the said\Vheatstonc bridge is an adjustable resistance, NV, which may be set atthat point to which it is desired to reduce the resistance ot' thecarbon strip G. At the same moment that the branches A A2 of the eut-outlever close the circuit by contact with the parts F F the part L, at theother end ofthe cut-out lever, touches the contact-piece L' and closesthe circuit of the galvanometer G through the connections M M and thebranch A of the cutout lever. The three parts A A A2 of the lever areinsulated one from another by the insulatingblock I. The Vheatstoncbridge is supplied by a suitable current from the battery B. Throughoutthe apparatus the current follows the direction indicated by the arrows.

It will be seen that while the testing portion of my apparatusis idlethe circuitthrough the galvanometer is broken, and that such circuit isonly closed at the Very moment when the resistance which is .to bedctcrmincdisintroduced into one branch of the Vheatstone bridgeconnection. Thus a galvanometer of the most delicate construction may beused, and its adjustment is not destroyed by continued passage of thecurrent through its coils with the usual heating effect. Moreover, asthe carbon strip is not removed during the operation, there is nopossibility of breaking it, and if the process of varying its resistancehas not been carried sufficiently far, as shown by the test, it isresumed without 'interruption by simply withdrawing all pressure fromthe button at one end of the cutout lever, when" the greater weight ofthe other end ol' the lever in the construction shown will cause it toassume the position shown in the drawings, andthe source of current, D,will again be thrown into the circuit. Ot' course it would be possibleto accelerate the action of the key or cut-out lever by means of aspring in the ICO usual way, which is too well understood to needillustration.

The carbon strip Gandits connections leading to the cut-out lever I callthe work-circuit, while the dynamo D, or its equivalent, and itsconnections lead ing to the cut-ont lever I call the main-current-supplycircuit.

VhileI haveshown and described, as above, the adaptation of my inventionto that particular arrangement of sub-circuits in shunt relation one toanother, which constitute what is called a Wheatstone bridge,7 it mayevidently be applied to any arrangement of subcircuits within theelectrical or magnetic field of which a tell-tale or indicating deviceis placed. Thus in that portion ofthe figure drawn in dotted lines Ihave illustrated its application to another arrangement of sub-circuitswhich operate on the ordinary form of different galvanometer.

In the modification thus shown in dotted lines the current for testingpurposes is supplied from the battery b. When the cut-out lever ispressed down, the current follows the respective directions indicated bythe arrows. A part goes over the line V', through the work-circuit ofthe carbon strip C, as before described, along the line V, through onecoil, c', of the differential galvanorneter, through the connections q'and m to the part A of the cut-out lever, thence through the contacts Land L and the connection m back to the other pole of the battery b. Asecond part of the circuit is shunted over the branch p, through theadjustable resistance w, and the other coil c of the differentialgalvanometer back by the connection q and line m', through the cut-outlever,along the path before traced to the other pole of the battery.

As the resistance of the carbon strip C is greater or less than that ofthe ascertained resistance w, lcssormore current will go through thecoils c and c and the galvanometerneedle g will move under the influenceof the preponderating coil. An advantage possessed by this particulararrangement is that the battery b is kept on open circuit at all timeswhen not engaged in the actual useful work of testing, and therefore itsenergy is cconomized to the highest possible degree.

Having therefore described my invention both in essence and detail, whatI claim as new, and desire to protect by Letters Patent, 1s-

l. In an apparatus for electrical testing, the combination ofthework-circuit, the main-current-supply circuit, and a Wheatstone bridgesupplied with an independent current from a second source, together witha suitable cutout, which, by one movement of the lever,cuts out thework-circuit from the main source of supply, throws it into circuit withone branch of the W'heatstone bridge, and simultaneously closes thegalvanometer-circuit of the bridge, substantially as described.

2. In anapparatus for electrical testing, a Vheatstone bridge, having anascertained resistance in one of its branches, while the circuit throughits second branch and the circuit through its galvanometer are normallybroken, together with a cutout, which, by one motion of the lever,simultaneously closes the galvanometer-circuit and introduces into thesecond branch of the bridge the unknown resistance which is to betested, all in combination, substantially as described.

3. In an apparatus for electrical testing, the combination oftheworlccircuit, the main-current-supply circuit, and an arrangement ofsub-circuits placed in shunt relation to each other,iu one of whichsub-circuits there is an ascertained resistance, and acurrent-indicating device within the influence of the currents iowing inthe said sub-circuits, together with a suitable cutout, which,by onemovement of the lever, cuts ont the work-circuit from the main source ofsupply, throws it into one of the subcircuits, and simultaneously closesthe remaining sub circuits, whereby the resultant effect ofthe currentsthus shunted through the various sub-circuits will show by thecurrentindicating device the relation of the work-circuit resistance tothe ascertained resistance, substantially as described.

4. In an apparatus for electrical testing, the combination ot'awork-circuit, a main-currentsupply circuit, and an arrangement ofsubcircuits such as shall constitute an indicating or tell-tale device,together with a suitable cutout, which,by one motion of the lever,cutsout the Work-circuit from the main-current-supply circuit and throws thework-circuit into connection with the tell-tale device at the same timethat it closes allof those subfcircuits constituting the tell-taledevice which are normally open, substantially as described.

In testimony whereof I affix my signature in presence of witnesses.

JAMES WARD PACKARD.

Witnesses:

W. D. PACKARD, ED. BEEsLEY.

